High-precision blind hole bottom numerical control machining method
By precisely coordinating boring and end milling cutters, residual curved surfaces are created and line cutting is performed, solving the problem of residual steps at the bottom of high-precision blind holes, improving surface quality and part life, and reducing the difficulty of fitter operations.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHENGDU AIRCRAFT INDUSTRY GROUP
- Filing Date
- 2026-02-10
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies cannot effectively eliminate the residual machining steps at the bottom of high-precision blind holes, leading to stress concentration and shortened fatigue life. Furthermore, manual grinding presents quality risks and operational difficulties.
By using CNC machining methods and precise coordination of boring tools and end mills, residual curved surfaces are created and line cutting is performed to eliminate the residual steps at the bottom of blind holes.
It improves the surface quality of blind holes, reduces the risk of tool grinding, reduces operational difficulty, ensures the integrity of the inner wall and bottom of the hole, and extends the fatigue service life of the parts.
Smart Images
Figure CN122007808A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of CNC machining technology, specifically relating to a high-precision CNC machining method for the bottom of blind holes. Background Technology
[0002] With the continuous development of the aviation industry, the precision requirements for assembly connections in engineering are getting higher and higher, and the fatigue strength requirements for assembly connection parts are also getting higher and higher. The assembly connection area is often connected by various high-precision holes on the parts. Correspondingly, the requirements for the hole position accuracy, hole diameter accuracy and inner wall surface quality of the high-precision holes in the assembly connection area of the parts are also getting higher and higher.
[0003] Among them, high-precision blind holes, as a type of assembly connection hole, are structurally characterized by an inner wall, a bottom, and a bottom angle R. Figure 1 As shown, the surface quality and diameter accuracy of the inner wall of the hole are required to be extremely high, with a diameter accuracy of IT8 or higher and a surface roughness of Ra1.6 or higher.
[0004] The machining of the inner wall of such holes often involves a series of steps: milling the initial hole with an end mill, machining the inner wall with a boring tool, further milling the remaining material at the bottom of the hole with an end mill, and then grinding the remaining material at the bottom of the hole and machining steps by a fitter. During CNC machining, the material and the tool are squeezed against each other, and the elastic variables of both are important factors affecting the machining accuracy. The boring tool diameter can be adjusted according to the actual elastic variables of different materials and structures of the parts to reduce the influence of the elastic variables of the parts and the boring tool on the hole diameter during the machining process, thereby achieving high-precision machining of the inner wall of the hole.
[0005] The bottom and bottom corner radius (R) of a hole are often machined using a CNC end mill. To prevent damage to the inner wall of the hole from the end mill, a small clearance distance is generally required in the CNC programming of the hole bottom. This results in a condition where, after machining a high-precision blind hole, a shape resembling a bevel or stubble appears at the bottom of the hole. Figure 2 Machining step residue is a common problem in engineering applications. In such cases, it can lead to stress concentration and cracking during repeated use, affecting the fatigue life of parts. Therefore, it is necessary to eliminate this residue. Conventional methods involve grinding by a fitter. However, grinding inside the hole presents several challenges: firstly, there is a risk of damaging the hole's inner wall during grinding; secondly, the limited space makes operation difficult for the fitter; thirdly, in cases of insufficient space, no grinding tools can be inserted deep into the hole; and fourthly, the surface quality after grinding is poor. Therefore, a high-precision CNC machining method for the bottom of blind holes is urgently needed in engineering applications to eliminate the machining step residue left after high-precision blind hole CNC machining and improve the surface quality of high-precision blind holes.
[0006] For example, a Chinese patent, publication number CN109604942A, publication date April 12, 2019, entitled "A CNC Machining Method for High-Precision Flat-Bottomed Hanging Holes in Aluminum Alloys," discloses the following technical solution: This invention discloses a CNC machining method for high-precision flat-bottomed hanging holes in aluminum alloys, specifically including the following steps: Step S1: Part clamping; Step S2: Initial hole machining; Step S21: Determining the diameter of the initial hole as φF and the diameter of the final hole as φ, wherein the diameters of the final hole and the initial hole satisfy: φ φF≥1mm and the initial hole and final hole are coaxial; Step S22: Select a milling cutter as the initial hole machining tool and perform initial hole machining by milling; The radius R of the bottom tooth of the milling cutter is consistent with the diameter φR of the bottom corner of the hole, and the length-to-diameter ratio of the milling cutter is less than 4:1; Step S23: Machining; Specifically, it refers to: using a spiral down-cutting cutter for climb milling, the trajectory diameter of the spiral down-cutting cutter is greater than D / 4; The part is axially layered for machining, and the axial machining depth should meet: LG=LH; Where: D is the diameter of the milling cutter; LG is the axial machining depth of the initial hole; LH is the final hole depth; Step S3: Boring; Step S4: Root corner machining, completing the machining.
[0007] While the aforementioned patents can effectively improve the processing quality and efficiency of flat-bottomed hanging holes, they still cannot solve the technical problem of residual processing steps after CNC machining of the bottom of blind holes. Summary of the Invention
[0008] To address the problems existing in the prior art, this application provides a high-precision blind hole bottom CNC machining method that can eliminate the problem of residual machining steps after high-precision blind hole boring and end mill machining.
[0009] To achieve the aforementioned technical effects, the specific technical solution of this application is as follows: A high-precision CNC machining method for the bottom of a blind hole includes the following specific steps: Step S1: Based on the blind hole parameters, obtain the residual Z-axis height of the bottom corner of the blind hole and the effective depth of the boring tool. Step S2: Based on the boring tool parameters, obtain the bore diameter allowance before boring and the initial diameter of the blind hole; Step S3: Determine the radial adjustment range of the boring tool based on the initial diameter of the blind hole, the bottom angle of the end mill, and the blind hole diameter in the blind hole parameters; Step S4: Based on the bore diameter allowance before boring, the residual Z-axis height of the blind hole bottom angle, and the blind hole bottom angle in the blind hole parameters, create the residual surface of the blind hole bottom angle; Step S5: After checking the Z-axis height of the end mill, use the end mill to machine the initial hole of the blind hole according to the initial hole diameter; Step S6: After checking the Z-axis height of the boring bar, use the boring bar to machine the diameter of the blind hole according to the effective depth of the boring bar. Step S7: Adjust the boring tool to the minimum diameter and perform line cutting based on the residual curved surface at the bottom corner of the blind hole, so that there is no machining step residue at the bottom of the boring hole.
[0010] Furthermore, the blind hole parameters also include the blind hole depth.
[0011] Furthermore, the effective depth of the boring tool and the residual Z-axis height of the blind hole bottom angle are calculated using the blind hole bottom angle and the blind hole depth.
[0012] Furthermore, the specific calculation formula for the residual Z-axis height at the bottom corner of the blind hole is as follows: h1 = R + h3; In the formula, h1 means the residual Z-direction height at the bottom corner of the blind hole, and h3 means the residual area height h3 on the inner wall of the hole.
[0013] Furthermore, the effective depth of the boring bar is less than the blind hole depth minus the blind hole bottom angle, thus forming the height of the residual area on the inner wall of the hole; the residual height on the inner wall of the hole is specifically obtained by subtracting the blind hole bottom angle from the blind hole depth, and then subtracting the effective depth of the boring bar; the calculation formula for the effective depth of the boring bar is as follows: h2 = hR - h3; In the formula, h2 means the effective depth of boring; h means the depth of blind hole; R means the bottom angle of blind hole; h3 means the height of the residual area on the inner wall of the hole, which is 0.1 mm to 0.2 mm.
[0014] Furthermore, the boring tool parameters include the radial cutting edge length of the boring tool; the pre-boring diameter allowance and the initial diameter of the blind hole in step S2 are calculated using the radial cutting edge length of the boring tool; the radial cutting edge length of the boring tool is 0.3 mm to 0.5 mm greater than the pre-boring diameter allowance, and the specific calculation formula is as follows: δ = L1 - δ1; In the formula, δ means the bore diameter allowance before boring; L1 means the radial cutting length of the boring tool; δ1 means the value where the radial cutting length of the boring tool is greater than the bore diameter allowance before boring.
[0015] Furthermore, the specific formula for calculating the initial diameter of the blind hole in step S2 is as follows: D1=D-2×δ=D-2×(L1-δ1); In the formula, D1 represents the initial diameter of the blind hole, D represents the diameter of the blind hole, and δ represents the diameter allowance before boring.
[0016] Furthermore, the radial adjustment range of the boring tool in step S3 is specifically as follows: the maximum diameter of the boring tool adjustment is greater than the diameter of the blind hole, and the minimum diameter of the boring tool adjustment is less than the initial diameter of the blind hole minus twice the bottom angle of the end mill; the bottom angle of the end mill is greater than or equal to the diameter of the blind hole; the specific relationship of the minimum diameter of the boring tool adjustment is as follows: DL <D1-2×R1; In the formula, DL means the minimum diameter of the boring tool; D1 means the initial diameter of the blind hole; and R1 means the bottom angle of the end mill.
[0017] Furthermore, the residual curved surface of the blind hole bottom corner includes the blind hole bottom corner, the residual area at the bottom of the blind hole, and the height of the residual area on the inner wall of the hole; the residual area at the bottom of the blind hole is the residual radial length of the blind hole bottom corner, and the residual radial length of the blind hole bottom corner is equal to the hole diameter allowance before boring; the height of the residual area on the inner wall of the hole is equal to the residual Z-direction height of the blind hole bottom corner minus the blind hole bottom corner.
[0018] Furthermore, in step S4, the residual surface of the blind hole bottom corner is created by using the Isoparametric Machining operation; in step S7, the residual surface of the blind hole bottom corner is called by using Isoparametric Machining and the residual surface of the blind hole bottom corner is subjected to line cutting processing.
[0019] Based on the above technical solution, the beneficial effects of the present invention are as follows: 1. Compared with the prior art, the method of this invention solves the problem of residual machining steps formed after high-precision blind hole boring and end milling, improves the surface quality of high-precision blind holes, reduces the quality risk of bench grinding in the prior art, and reduces the workload of bench workers.
[0020] 2. The method of the present invention ensures that there are no machining steps remaining on the bottom surface of the blind hole after it has been machined by the boring tool and end mill by checking the Z-axis height of the boring tool and end mill.
[0021] 3. The method of the present invention obtains the initial diameter of the blind hole based on the boring tool parameters, which can ensure that when the boring tool is processed to the bottom of the hole, the bottom processing step residue will not scratch the bottom of the boring tool bar.
[0022] 4. The design requirement for adjusting the minimum diameter of the boring tool in the method of the present invention can ensure that after the diameter of the boring tool is adjusted to the minimum, the cutting edge of the boring tool can completely eliminate the machining step residue at the bottom of the blind hole, thereby improving the quality of the surface of the high-precision blind hole.
[0023] 5. In this invention, a boring tool is used to process the residual machining steps at the bottom of the blind hole. Because the tool clamping state and the part state are consistent, and the same tool is used to process the inner wall and bottom surface of the hole, the rigidity of the tool and the part does not change. Therefore, when using a boring tool to process the bottom corner residue, it is ensured that no machining step residue will be generated on the inner wall of the hole.
[0024] 6. This invention proposes using boring tools in the same way as end mills and employing a line cutting method to process residual bottom corners, which greatly reduces milling problems such as tool bounce and broaching during the residual machining process. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of a high-precision blind hole structure.
[0026] Figure 2 This is a schematic diagram of the residual step at the bottom of a blind hole after boring.
[0027] Figure 3 This is a schematic diagram of a high-precision blind hole with parameter symbols.
[0028] Figure 4 This is a schematic diagram of the structure of a boring bar and an end mill.
[0029] Figure 5 This is a schematic diagram of the cross-section of a high-precision blind hole.
[0030] Figure 6 This is the intention of the toolpath in the cutting program. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.
[0032] Example 1 A high-precision CNC machining method for the bottom of a blind hole includes the following specific steps: Step S1: Based on the blind hole parameters, obtain the residual Z-axis height of the bottom corner of the blind hole and the effective depth of the boring tool. Step S2: Based on the boring tool parameters, obtain the bore diameter allowance before boring and the initial diameter of the blind hole; Step S3: Determine the radial adjustment range of the boring tool based on the initial diameter of the blind hole, the bottom angle of the end mill, and the blind hole diameter in the blind hole parameters; Step S4: As Figure 5 As shown, based on the bore diameter allowance before boring, the residual Z-axis height of the blind hole bottom angle, and the blind hole bottom angle in the blind hole parameters, a residual surface of the blind hole bottom angle is created. Step S5: After checking the Z-axis height of the end mill, the effective working length of the end mill must be greater than the blind hole depth. Machin the initial hole of the blind hole using the end mill according to the initial hole diameter; the machining depth of the initial hole of the blind hole using the end mill shall be performed according to the blind hole depth. Step S6: After checking the Z-axis height of the boring bar, the effective working length of the boring bar must be greater than the depth of the blind hole. The boring bar is used to machine the diameter of the blind hole according to the effective depth of machining. The purpose of this check is to ensure that there will be no tool contact error when the boring bar is used to machine the bottom of the blind hole in the next step. Step S7: Adjust the boring bar to its minimum diameter and perform slicing based on the residual curved surface at the bottom corner of the blind hole, thus eliminating any machining steps at the bottom of the bored hole. The boring bar's adjustment mechanism moves its tip in the diameter direction, adjusting the diameter formed by the boring bar's rotation during use. Since the high-precision blind hole's inner wall and bottom corner R are machined using the same boring bar, the elastic variables of the tool and the material being cut do not change during the cutting process. Therefore, after the boring bar's slicing, no machining steps will be formed as described above. Figure 2 The steps shown are remnants.
[0033] like Figure 3 As shown in the attached figure, D is the diameter of the blind hole, D1 is the initial diameter of the blind hole, δ is the diameter allowance before boring, h2 is the effective depth of boring, h is the depth of the blind hole, h1 is the residual Z-axis height of the bottom corner of the blind hole, L2 is the residual radial length of the bottom corner of the blind hole, h3 is the height of the residual area on the inner wall of the hole, and R is the bottom corner of the blind hole.
[0034] The inspection and adjustment of the boring bar and end mill in the above steps are conventional existing techniques in this field and will not be described in detail here.
[0035] Example 2 Based on Example 1, the blind hole parameters also include the blind hole depth; the effective depth of the boring tool and the residual Z-axis height of the blind hole bottom corner are calculated using the blind hole bottom corner and the blind hole depth. The specific calculation formula for the residual Z-axis height of the blind hole bottom corner is as follows: h1 = R + h3; In the formula, h1 represents the residual Z-axis height at the bottom corner of the blind hole, and h3 represents the height of the residual area on the inner wall of the hole.
[0036] like Figure 1 As shown, to ensure that the bottom corner of a high-precision blind hole is not damaged during boring, the effective depth of the boring tool is less than the depth of the blind hole minus the bottom corner, thus creating a residual height on the inner wall of the hole. This residual height is specifically obtained by subtracting the bottom corner (R) of the high-precision blind hole from the depth of the blind hole, and then subtracting the effective depth of the boring tool. The formula for calculating the effective depth of the boring tool is as follows: h2 = hR - h3; In the formula, h2 means the effective depth of boring; h means the depth of blind hole; R means the bottom angle of blind hole, which is the radius of the arc; h3 means the height of the residual area on the inner wall of the hole, which is 0.1mm to 0.2mm.
[0037] like Figure 4 As shown, the boring tool parameters include the radial cutting edge length; the bore diameter allowance before boring and the initial diameter of the blind hole in step S2 are calculated using the radial cutting edge length of the boring tool; to ensure that the residue at the bottom of the hole does not touch the bottom of the boring tool shank during boring, the radial cutting edge length of the boring tool should be 0.3mm to 0.5mm greater than the bore diameter allowance before boring, and the specific calculation formula is as follows: δ = L1 - δ1; In the formula, δ means the bore diameter allowance before boring; L1 means the radial cutting length of the boring tool; δ1 means the value where the radial cutting length of the boring tool is greater than the bore diameter allowance before boring.
[0038] The specific formula for calculating the initial diameter of the blind hole in step S2 is as follows: D1=D-2×δ=D-2×(L1-δ1); In the formula, D1 represents the initial diameter of the blind hole, D represents the diameter of the blind hole, and δ represents the diameter allowance before boring.
[0039] The specific radial adjustment range of the boring bar in step S3 is as follows: the maximum diameter of the boring bar adjustment is greater than the diameter of the blind hole, and the minimum diameter of the boring bar adjustment is less than the initial diameter of the blind hole minus twice the bottom angle of the end mill; the bottom angle of the end mill is greater than or equal to the diameter of the blind hole; the specific relationship of the minimum diameter of the boring bar adjustment is as follows: DL <D1-2×R1; In the formula, DL means the minimum diameter of the boring tool; D1 means the initial diameter of the blind hole; and R1 means the bottom angle of the end mill.
[0040] The residual surface at the bottom corner of a blind hole includes the bottom corner of the blind hole, the residual area at the bottom of the blind hole, and the height of the residual area on the inner wall of the hole; such as Figure 1 As shown, to ensure that the residue at the bottom of the high-precision blind hole can be completely removed, the residual area at the bottom of the blind hole is equal to the radial length of the residual area at the bottom corner of the blind hole, and the radial length of the residual area at the bottom corner of the blind hole is equal to the hole diameter allowance before boring; the height of the residual area on the inner wall of the hole is equal to the Z-axis height of the residual area at the bottom corner of the blind hole minus the bottom corner of the blind hole. To ensure that the residue at the bottom of the hole can be completely removed, the residual area at the bottom of the blind hole can be appropriately extended 0.2mm towards the center of the blind hole, such as... Figure 5 The extension line shown.
[0041] like Figure 6As shown, in step S4, the residual surface of the blind hole bottom corner is created by using the Isoparametric Machining operation; in step S7, the residual surface of the blind hole bottom corner is called by using Isoparametric Machining, and the residual surface of the blind hole bottom corner is processed by line cutting.
[0042] Example 3 Based on Example 2, this application provides a specific application example using the processing of a certain part as an example: S1: Basic characteristics of high-precision blind holes: High-precision blind hole diameter D=70mm; High-precision blind hole depth h=40mm; Blind hole bottom angle R=3mm; Boring tool radial cutting length L1=1mm; S2: Calculate the residual Z-axis height h1 at the bottom corner of the blind hole and the effective depth h2 of the boring tool: h3=0.2mm; h1=R+h3=3.2mm; h2=h-h1=36.8mm; S3: Calculate the bore diameter allowance δ and the initial bore size D1 before boring: δ = L1 - 0.5mm = 2.5mm; D1 = D - 2 × (L1 - 0.5mm) = 70 - 2 × 0.5 = 69mm; S4: Determine the radial adjustment range of the boring bar (minimum diameter DL for boring bar adjustment, maximum diameter DH for boring bar adjustment): R1=R=3mm; DH>70mm; DL <D1-2×R1-1mm=69-2×3-1=62mm; S5: Create the residual surface Q at the bottom corner of the blind hole: L2=δ=2.5mm; Z-axis height of residual surface Q=R+h3=3.2mm; Radial length of residual surface Q=R+L2+0.2=3.7mm; S6: Based on the minimum adjustment diameter of the boring bar (62mm), establish the end mill model. Use the Isoparametric Machining operation with a traverse distance of 0.005mm to create a traverse machining program for the residual surface Q. The traverse machining program speed is given according to the end mill machining parameters. See the schematic diagram of the traverse machining program. Figure 6 As shown.
[0043] S7: Processing procedure: Use an end mill with a bottom angle of 3mm to machine the initial blind hole. Before machining, strictly check the Z-axis height of the tool to ensure the accuracy of the blind hole depth. Use a boring bar to machine the diameter D of the blind hole, with an effective boring depth of 36.8mm. Before machining, strictly check the Z-axis height of the tool to ensure that there will be no tool contact error when machining the bottom of the blind hole with the boring bar in the next step. Adjust the boring bar to its minimum diameter of 62mm, and call the line cutting program for the residual curved surface Q to perform line cutting on the residual bottom corner of the blind hole. Since the inner wall and bottom corner R of the high-precision blind hole are machined using the same boring bar, the elastic variables of the tool and the material being cut do not change during the cutting process of the inner wall and bottom corner R. Therefore, after the boring bar's line cutting, no defects will form. Figure 2 The steps remain.
[0044] The above description is a detailed description of the preferred embodiments of this application. However, the embodiments are not intended to limit the scope of the patent application of this application. All equivalent changes or modifications made under the technical spirit of this application should fall within the patent scope covered by this application.
Claims
1. A high-precision CNC machining method for the bottom of a blind hole, characterized in that, The specific methods and steps include the following: Step S1: Based on the blind hole parameters, obtain the residual Z-axis height of the bottom corner of the blind hole and the effective depth of the boring tool. Step S2: Based on the boring tool parameters, obtain the bore diameter allowance before boring and the initial diameter of the blind hole; Step S3: Determine the radial adjustment range of the boring tool based on the initial diameter of the blind hole, the bottom angle of the end mill, and the blind hole diameter in the blind hole parameters; Step S4: Based on the bore diameter allowance before boring, the residual Z-axis height of the blind hole bottom angle, and the blind hole bottom angle in the blind hole parameters, create the residual surface of the blind hole bottom angle; Step S5: After checking the Z-axis height of the end mill, use the end mill to machine the initial hole of the blind hole according to the initial hole diameter; Step S6: After checking the Z-axis height of the boring bar, use the boring bar to machine the diameter of the blind hole according to the effective depth of the boring bar. Step S7: Adjust the boring tool to the minimum diameter and perform line cutting based on the residual curved surface at the bottom corner of the blind hole, so that there is no machining step residue at the bottom of the boring hole.
2. The high-precision CNC machining method for the bottom of a blind hole according to claim 1, characterized in that: The blind hole parameters also include the blind hole depth.
3. The high-precision CNC machining method for the bottom of a blind hole according to claim 2, characterized in that: The effective depth of the boring tool and the residual Z-axis height of the blind hole bottom angle are calculated using the blind hole bottom angle and the blind hole depth.
4. The high-precision CNC machining method for the bottom of a blind hole according to claim 3, characterized in that: The specific formula for calculating the residual Z-axis height at the bottom corner of the blind hole is as follows: h1 = R + h3; In the formula, h1 means the residual Z-direction height at the bottom corner of the blind hole, and h3 means the residual area height h3 on the inner wall of the hole.
5. A high-precision CNC machining method for the bottom of a blind hole according to claim 4, characterized in that: The effective depth of the boring bar is less than the blind hole depth minus the blind hole bottom angle, thus forming the height of the residual area on the inner wall of the hole. Specifically, the residual height is obtained by subtracting the blind hole bottom angle from the blind hole depth, and then subtracting the effective depth of the boring bar. The formula for calculating the effective depth of the boring bar is as follows: h2 = hR - h3; In the formula, h2 means the effective depth of boring; h means the depth of blind hole; R means the bottom angle of blind hole; h3 means the height of the residual area on the inner wall of the hole, which is 0.1 mm to 0.2 mm.
6. A high-precision CNC machining method for the bottom of a blind hole according to claim 5, characterized in that: The boring tool parameters include the radial cutting edge length; the bore diameter allowance before boring and the initial diameter of the blind hole in step S2 are calculated using the radial cutting edge length of the boring tool; the radial cutting edge length of the boring tool is 0.3 mm to 0.5 mm greater than the bore diameter allowance before boring, and the specific calculation formula is as follows: δ = L1 - δ1; In the formula, δ means the bore diameter allowance before boring; L1 means the radial cutting length of the boring tool; δ1 means the value where the radial cutting length of the boring tool is greater than the bore diameter allowance before boring.
7. A high-precision CNC machining method for the bottom of a blind hole according to claim 6, characterized in that: The specific formula for calculating the initial diameter of the blind hole in step S2 is as follows: D1=D-2×δ=D-2×(L1-δ1); In the formula, D1 represents the initial diameter of the blind hole, D represents the diameter of the blind hole, and δ represents the diameter allowance before boring.
8. A high-precision CNC machining method for the bottom of a blind hole according to claim 7, characterized in that: The radial adjustment range of the boring bar in step S3 is specifically as follows: the maximum diameter of the boring bar adjustment is greater than the diameter of the blind hole, and the minimum diameter of the boring bar adjustment is less than the initial diameter of the blind hole minus twice the bottom angle of the end mill; the bottom angle of the end mill is greater than or equal to the diameter of the blind hole; the specific relationship of the minimum diameter of the boring bar adjustment is as follows: DL <D1-2×R1; In the formula, DL means the minimum diameter of the boring tool; D1 means the initial diameter of the blind hole; and R1 means the bottom angle of the end mill.
9. A high-precision CNC machining method for the bottom of a blind hole according to claim 8, characterized in that: The residual curved surface of the bottom corner of the blind hole includes the bottom corner of the blind hole, the residual area at the bottom of the blind hole, and the height of the residual area on the inner wall of the hole; the residual area at the bottom of the blind hole is the residual radial length of the bottom corner of the blind hole, and the residual radial length of the bottom corner of the blind hole is equal to the hole diameter allowance before boring; the height of the residual area on the inner wall of the hole is equal to the residual Z-direction height of the bottom corner of the blind hole minus the bottom corner of the blind hole.
10. A high-precision CNC machining method for the bottom of a blind hole according to claim 9, characterized in that: In step S4, the residual surface of the blind hole bottom corner is created by using the Isoparametric Machining operation; in step S7, the residual surface of the blind hole bottom corner is called by using Isoparametric Machining and the residual surface of the blind hole bottom corner is processed by line cutting.